Absorption chillers comprise a condenser, evaporator, absorber, generator, heat exchanger, etc. which are interconnected by piping. The generator is equipped with a combustion system for heating lithium bromide or like absorbent having absorbed a refrigerant to concentrate the absorbent. For example, a fuzzy control system has been proposed for controlling such absorption chillers (U.S. Pat. No. 5,224,352).
With reference to FIG. 2, the combustion system provided for the generator of the absorption chiller comprises a main burner 15 installed in a combustion chamber 10, a pilot burner 17 for igniting the main burner 15 and a spark rod 20 for igniting the pilot burner 17. First, the spark rod 20 generates a spark, igniting the pilot burner 17, and the flame produced by the pilot burner 17 ignites the main burner 15.
Operated in a predetermined sequence in this process are a plurality of devices constituting the combustion system which include an ignition transformer 19 for causing the spark rod 20 to produce sparks, and pilot valves 16 and main valves 12, 13 for supplying a fuel to the respective burners.
The flames produced by the main burner and pilot burner and the spark generated by the spark rod are detected by a flame sensor 21, and the resulting detection signals are incorporated into the operation sequence.
With the combustion system thus comprising a plurality of devices, failures could occur during the predetermined sequence of operations of the devices. In this case, a failure will exert influences of varying intensities on various items of measurement data representing the behavior of the devices, e.g., the time (spark detection time) from the application of voltage to the ignition transformer until the spark rod produces a spark, the current flowing through the primary side of the ignition transformer, and the flame current produced from the flame sensor.
Upon the combustion system developing some failure, therefore, the maintenance inspector observes variations in the measurement data with the progress of the combustion system operation sequence to diagnose the cause of the failure.
With the combustion system, however, not only one failure influences a plurality of items of measurement data with varying intensities, but a plurality of different failures will occur at the same time, synergically affecting a single item of measurement data, or one failure could influence different items of measurement data owing to a difference in the state of failure. Diagnosing the causes of failures based on the observation of measurement data therefore requires a long experience and sophisticated knowledge. For this reason, inspectors of small Experience encounter the problem of necessitating much time in determining the causes of failures owing to extreme difficulties involved in diagnosis.